The idea of a giant asteroid causing untold destruction has inspired countless disaster movies, but it's never really been considered a threat to humanity. Now, scientists at the University of Valladolid in Spain have warned that a giant asteroid really might be on course to collide with our planet — but not until 2182. (Watch a report, heavy on theatrics, on the asteroid threat.) Here's a quick guide to the asteroid on its way to Earth:

What are the odds of this asteroid hitting Earth?The rock, which has been given the catchy title of "(101955) 1999 RQ36," has a one in 1,000 chance of impacting Earth on Sept. 24, 2182. Given the enormity of space, those are extremely high odds of impact, especially as there is still uncertainty as to its exact trajectory. Scientists will not be sure whether it will hit us until 2082.

How big is it?The asteroid is about 612 yards wide, according to scientists. If that doesn't sound very large, consider that the last significant piece of space debris to hit earth — the Tunguska comet, in 1908 — destroyed 830 square miles of Siberian forest. This asteroid is about 10 times larger.

How big would an asteroid have to be to end life on Earth?Any asteroid over 1,000 yards in width would create a nuclear winter, killing all plant life on the planet and likely all human life, too. The asteroid blamed for wiping out the dinosaurs is thought to have been 7.5 miles wide. The largest asteroid discovered by human scientists is roughly 18 miles wide. If that struck Earth, it would eradicate all but microbiotic life.What can we do to stop this one?Nothing just yet. It would be moving far too quickly — around 25 kilometers a second — for any currently available technology to change its path. Only when scientists are sure it will impact on earth will "technologically and financially feasible" ways to destroy or deflect it be examined. In other words, it's a bit too early to deploy Bruce Willis.

Are there any other asteroids on their way here?A 328-yard asteroid will hurtle past Earth on April 13, 2029 (yes, it's a Friday). The rock, known as Apophis, is expected to miss the planet by just 18,300 miles — that's closer than most TV satellites orbiting the Earth. If it did hit, the force would be 65,500 times stronger than the atomic bomb dropped on Hiroshima. But the odds it will alter course to impact on us are around one in 250,000.

Why are we only finding out about this now?Actually, the University of Valladolid discovered 1999 RQ36 last year, and the news only just caught the attention of the Spanish Foundation for Science and Technology, which put out a press release. "Whether this asteroid’s path is old news or not, we shouldn’t dawdle in thinking about how we might avoid it or asteroids like it," says Discovery Magazine's Andrew Moseman. "In this case, we’ve only got 172 years — and we already wasted one year getting the news out."